A variety of conveyor roller systems have been designed and utilized. A large variety of known conveyor systems comprise a continuous belt or conveyor medium which travels over a series of conveyor rollers.
Early conveyor roller systems utilized at least one conveyor drive roller which was driven by an electric motor positioned outside of, and connected to, the conveyor drive roller typically via a chain or rubber belt, and often with an external gear assembly positioned between the motor and the conveyor roller. The conveyor drive roller thereby translated the rotational movement of the electric motor to linear movement of the conveyor medium. The main disadvantage of these early designs, which are still utilized today, is that they take up a lot of space. However, the exposed moving parts also pose a hazard to workers, especially the external gear assembly and chain from the external gear assembly to the conveyor roller, which output high levels of torque, as compared to the motor on its own. The exposed moving parts also pick up debris which damages the conveyor roller system.
In later conveyor roller systems, the electric motor was arranged within the conveyor drive roller to provide a more compact conveyor roller system as taught, for example, in U.S. Pat. No. 1,725,740 to Schulte.
An example of an even more advanced conveyor drive roller is disclosed in U.S. Pat. No. 5,088,596 to Agnoff, which teaches a motorized conveyor drive roller mounted in a conveyer frame to support and propel articles from one end of the conveyor path towards the opposite end. The Agnoff conveyer drive roller includes a roller tube rotatably mounted in the conveyor frame and drive means contained inside the roller tube for driving the roller tube. The drive means includes a motor, a gear reducer assembly operatively connected to the motor, and a drive member connected to the outward shaft of the speed reducer for engaging and rotating the roller tube.
Conveyor roller systems having conveyor drive rollers which are driven by motor and gear combinations, contained entirely within the conveyor drive roller itself, are of particular utility in many applications. The internal motor and gear system makes for a compact, space saving installation. Furthermore, the linear arrangement of the motor and gearing within the conveyor drive roller means that the transmission of power from the motor to the roller is carried out more directly resulting in higher levels of efficiency than is possible in conventional conveyor roller systems where the motor is located externally to the conveyor drive roller, especially where the axis of rotation of the rotor is at a 90° angle to the axis of rotation of the roller. The internal motor and gear combination also largely eliminates the risk of accident caused by contact with employees. Furthermore, it eliminates contamination of the motor/gear drive from dust and debris in the environment in which it is running, thereby greatly reducing maintenance, and the likelihood of failure, all of which results in less down time for the conveyor system.
All of these factors make the use of such conveyor drive rollers particularly useful and desirable. However, they also have disadvantages.
One such disadvantage is that while the likelihood of failure of such a conveyor drive roller is decreased, when it does fail servicing is very difficult and expensive, since it requires the shutting down of the conveyor roller system, removal of the entire defective conveyor drive roller (which is quite heavy since it contains the motor and gearing), which is then sent elsewhere for servicing. The conveyor roller system remains shut down until a new or repaired conveyor drive roller is installed in the conveyor system in place of the removed, defective one. Since conveyor drive rollers of this type (i.e. having the motor and gearing within them) are fairly expensive, companies that employ conveyor systems which utilize them typically do not stock spare conveyor drive rollers. This means that the conveyor system remains shutdown until the defective conveyor drive roller is repaired and re-installed.
Therefore, there is a need for improvement in the design of conveyor drive rollers.